Conventional bedding systems commonly include a mattress positioned upon and supported by a foundation or “box spring”. Foundations provide support and firmness to the mattress as well as some additional resilience in order to deflect under loads. Foundations are typically constructed of a frame, such as a rectangular frame including perimeter members and internal members or stringers, springs—such as steel wire springs—which are mounted upon the frame to extend upward from the frame and support a grid—such as a wire grid—above the frame. The grid serves as the primary structural support for the mattress, and in turn is flexibly supported by the springs. In order to adequately support the weight of the mattress and the loads placed upon the mattress, a dense distribution of springs is generally required. In conventional steel spring foundations, the springs are made of steel wire most commonly in torsion spring configurations, with bases or feet of the springs mounted directly to the interior frame members or stringers, and tops of the springs engaged with or otherwise fastened to the grid. The grid is typically a steel wire grid assembled with welds at orthogonal intersections of the wire and at a perimeter wire of heavier gauge.
Interestingly, although the perimeter or “border” wire of the grid is usually of substantially heavier gauge than the grid wires, in most foundations it is not directly supported by any of the springs, and as such is held by cantilevered support of the springs closest to the perimeter. As a result, such foundations actually provide the least reflexive vertical support at the perimeter region which contributes to the undesirable “roll-off” tendency, and is inadequate for the high perimeter loads when the edge of the mattress is used as a seat, which it frequently is. Although some efforts have been made to provide direct vertical support to the border wire, for example in the form of perimeter spring elements which extend from the perimeter frame members to the border wire, this can result in segments of the border wire which are less flexible than others, and adds component and manufacturing cost to the product.